The present disclosure relates generally to demoting network traffic to provide QoS (Quality of Service) for voice or mission critical traffic during a network failure.
An important requirement for migrating PSTN (public switched telephone network) voice services to IP networks is to provide the same levels of quality for voice services that are currently available with PSTN. A number of techniques are available to provide very tight QoS in the absence of failure, however, none of these voice load control approaches perform very well during a network failure. Thus, providing strict QoS to voice during network failure still remains an open problem in large scale voice deployment where the proportion of voice traffic is high.
A desired mechanism to provide tight QoS to voice services in IP networks has the ability to provide deterministic end-to-end admission control. In order to maintain QoS (or mitigate QoS degradation) it is important to provide rapid recovery around network failures. A number of techniques are available to provide very fast recovery in case of failure. However, with rapid recovery there is not enough time to make a new admission control decision before rerouting traffic due to a network failure. Thus, congestion may occur in the transient period before call admission control is performed again after the traffic rerouting.
There are only limited options currently available for protecting QoS over the period during which fast recovery mechanisms are in use. One option is to allocate a large amount of capacity to make sure QoS of all targeted traffic can be maintained during any failure scenario. This requires a significant amount of bandwidth to be dedicated to backup paths to protect all voice traffic in all targeted failure scenarios. Another option is to accept that any flow from the targeted traffic may be degraded during a failure. This may cause congestion that affects both the original traffic and the rerouted traffic, thus resulting in QoS degradation for all the traffic flow.